In these cold winter months, it is important to make the most of our heating energy. Everyone knows that hot air rises and cold air sinks (its called convection) but in a large house, that can mean a lot of lost heat.

Heat sources on the first floor create heat that rises up the stairwell. This rising hot air can actually move a surprisingly large volume of air and heat to the second floor. The rising hot air causes a very slight overpressure on the second floor that pushes cold air down the stairs. The rising hot air also leaves a slightly lower air pressure on the lower floors, which balances out by sucking in cold outside air from around windows and doors. This, in turn, makes the thermostat, on the first floor, kick on sooner. This rapid heat exchange gets worse as the house gets bigger, warmer or there are more floors. If you can feel it get cooler as you descend the stairs or if it is too warm upstairs but just right downstairs, then you have this problem.

One way to help reduce this imbalance is to put a fan near the ceiling of the stairwell, pointing down. This will blow some of the rising hot air back down or, at least disrupt the rapid rise of hot air up the stairwell. Sealing off upstairs rooms will reduce the volume of air that can rise and also reduce the sources for cooler air to descend. If you think of heat and cold as liquids that want to rise and sink, respectively, then the goal is to stop their flow and to capture and concentrate the heated air where you need it most — and that saves money.